diff --git a/src/osmo_gsm_tester/powersupply_sispm.py b/src/osmo_gsm_tester/powersupply_sispm.py
new file mode 100644
index 0000000..91604b4
--- /dev/null
+++ b/src/osmo_gsm_tester/powersupply_sispm.py
@@ -0,0 +1,111 @@
+# osmo_gsm_tester: class defining a Power Supply object
+#
+# Copyright (C) 2018 by sysmocom - s.f.m.c. GmbH
+#
+# Author: Pau Espin Pedrol <pespin@sysmocom.de>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import sispm
+from usb.core import USBError
+
+from . import log, event_loop
+from .powersupply import PowerSupply
+
+class PowerSupplySispm(PowerSupply):
+    """PowerSupply implementation using pysispm.
+
+    The device object from sismpm is not cached into an attribute of the class
+    instance because it is actually a libusb object keeping the device assigned
+    to it until it destroyed, meaning it will block other users to use the whole
+    device until the object is released. Instead, we pick the object in the
+    smallest scope possible, and we re-try if we receive a "Resource Busy" error
+    because we know it will be available in short time.
+    """
+
+    def _retry_usberr(self, func, *args):
+        """Run function until it runs successfully, retry on spurious errors.
+
+        Sometimes when operating the usb device, libusb reports the following spurious exception:
+        [Errno 16] Resource busy -> This can appear if another instance is using the device.
+        [Errno 110] Operation timed out
+
+        Retrying after that it's usually enough.
+        """
+        while True:
+            try:
+                ret = func(*args)
+                return ret
+            except USBError as e:
+                    if e.errno == 16 or e.errno==110:
+                        self.log('skip usb error, retry', repr(e))
+                        event_loop.sleep(self, 0.1)
+                        continue
+                    raise e
+
+    def _get_device(self):
+        """Get the sispm device object.
+
+        It should be kept alive as short as possible as it blocks other users
+        from using the device until the object is released.
+        """
+        mydevid = self.conf.get('device')
+        devices = self._retry_usberr(sispm.connect)
+        for d in devices:
+            did = self._retry_usberr(sispm.getid, d)
+            self.dbg('detected device:', did)
+            if did == mydevid:
+                self.dbg('found matching device: %s' % did)
+                return d
+        return None
+
+
+########################
+# PUBLIC - INTERNAL API
+########################
+    def __init__(self, conf):
+        super().__init__(conf, 'sispm')
+        mydevid = conf.get('device')
+        if mydevid is None:
+            raise log.Error('No "device" attribute provided in supply conf!')
+        self.set_name('sispm-'+mydevid)
+        myport = conf.get('port')
+        if myport is None:
+            raise log.Error('No "port" attribute provided in power_supply conf!')
+        if not int(myport):
+            raise log.Error('Wrong non numeric "port" attribute provided in power_supply conf!')
+        self.port = int(myport)
+        device = self._get_device()
+        if device is None:
+            raise log.Error('device with with id %s not found!' % mydevid)
+        dmin = self._retry_usberr(sispm.getminport, device)
+        dmax = self._retry_usberr(sispm.getmaxport, device)
+        if dmin > self.port or dmax < self.port:
+            raise log.Error('Out of range "port" attribute provided in power_supply conf!')
+
+    def is_powered(self):
+        """Get whether the device is powered on or off."""
+        return self._retry_usberr(sispm.getstatus, self._get_device(), self.port)
+
+    def power_set(self, onoff):
+        """Turn on (onoff=True) or off (onoff=False) the device."""
+        if onoff:
+            self.dbg('switchon')
+            self._retry_usberr(sispm.switchon, self._get_device(), self.port)
+        else:
+            self.dbg('switchoff')
+            self._retry_usberr(sispm.switchoff, self._get_device(), self.port)
+
+
+# vim: expandtab tabstop=4 shiftwidth=4